Improved refined wood pulp and a method of improving it



Patented Aug. 10, 1954 IMPRGVED REFINE METHODOF I Kenneth Russell Gray,Shelton,

to" Rayoni'er Incorpo corporation ofDelaware WOOD PULP AND A MPROVING ITWash-a assignor rated, Shelton, Wash, a

No'Drawing. Application July 14, 1950,

Seria-FNO. 173,949

M'GIaimS; (Cl; 106-163.)

This invention: relatestar chemically prepared wood pulp such'as theso-called dissolving pulp, hereinafterpfor convenience; calledreline'dwoo'd pulp The invention has. for: anlobiecti the-provision' of an:improved refin'ed: wood pulp and a method of producing the same The:improved wood pulp offthe inven'tion is: especially suitable for themanufacture" of regenerated cellulose products by the. viscoseprocessan'dZ for: the: pro duction of. cellulose. derivatives: such as.cellulose acetate, etc.

The invention further relates to the; production of cellulosic'products: from refined wood pulp and aims to provide certainimprovements in carrying out one orm'ore of the processingsteps usedinthe production or. such products;

In one of its important aspects the invention relates to producing apulp" of uniform characteristics from different pulps having differentpercentages of unsaponifiable and saponifiable ether extractable matter.

I'nanother of its important aspects, the invention involves the use-ofrefined wood pulp as-a source of cellulose in'the preparation ofcellulosic solutions for the' viscose process and has for a particularobject the use of an unsaponifiable, oil soluble, interfacially activematerial of'synthetic origin to improve the emulsification or dispersionof non-miscible: opacifying agents in viscose solutions used'insp'inning filaments, particularly as regards stabilizing emulsionsproduced in the. presencevof anion-active emulsifying materials. Theinvention also generally brings about improvements in other processingsteps and may be used with bright as Welles opacified viscose.

Refined wood pulp consists mainly of cellulose with relatively smallamounts of non-cellulosic impurities, such as hemi-celluloses, fats,resins, waxes, high molecular weight alcohols, etc. A substantialportion of the non-cellulosic impurities is extractable with ether, andis hereinafter called the etherextract 01' the ether extractable matter.

I- have found that the: ether two distinctly different types ofmaterials which possess or can exert under appropriate conditionsinterfacially active properties and which have important effects on theprocessing qualities of the pulp in the production of cellul'osicproducts. These two classes are:

1. Ihe saponifiable' portion of the ether: extract (otherwise termedether extractable saponifiable matter) which is of the-nature of fattyandresin' acids either in the'free state or combined in such extractcontains forms as glycerides or esters of higher alcohols. Thesematerials in their saponified state are water soluble soaps, i. e., areanion active agents. (-Where numerical valuesfor saponifiable matter areherein given, such values refer to the total amount of fatty and resinacids, both in free and combined form.)

2. Another portion consisting of unsaponifiable materials which aresubstantially nonvolatile; insoluble in water and dilute caustic soda,soluble in oil; and interfacially active at an oil-water interface.These unsaponifiable,-. oil soluble,. interfacially active materials arein general. high molecular weight alcohols such as. phytosterol.(Phytosterol is the-genericname forsterols derived from vegetablesources.)

Part of thephytcsterol isintheform of saponifiable esters withhigherfatty acids. On saponifloat-ion these esters form soaps andliberate-free phytosterol. The phytosterol. itself? is, however,unsaponifiablewhether inf-rec or combined form. Furthermore, in thisconnection in. referring to the unsaponifiable portion. of the etherextract (otherwise termed ether extractable unsaponi fiable. matter)thereis-meant'all the water insoluble residue which in asaponificationtreatment does not-combine with caustic alkalies to form water solublesoaps, irrespective as. to whether such material is in f-ree. orcombined form inthe ether extract.-

As commonlyused and as referred to specifically herein, the. termsinterfacially active. applied toamaterialrefersto the materialbeingcapable of lowering the interfacial tension at an interfacebyvirtue of a positiveadsorption therein. The term surfaceactive materialrefers to a water soluble material which will specifically reduce theinterfacial tension at an air-water interface, such. a liquid-airinterfacial tension being commonly termed; the surface tension. By thetermanion active material ismeant a water soluble, ionizable surfaceactive material; the surface activity of. which is cluev to the anion;Such materialsmay be presentin the pulp'inan actually anion active form,or ina forum which is converted to a soap. by the action of alkali.

Naturally occurring unsaponifiable; oil soluble; interfaciallyactive-agents constitute alargefraction of the unsaponifiable The:unsaponifiablet ether. extractable matter also containsother: fractionssuch: as hydrocarbons and: chlorinated hydrocarbonswhich are notinterfaciall y active. Nevertheless the: amount. of totalunsaponifi'able ether extractable matter serves generally as a relativeindication of the amount of unsaponifiable, oil soluble, interfaciallyactive material and is a more easily determined value.

I have found that as regards difierent woods commonly used for producingpulp, such as pine, spruce, and hemlock, the ether. extract left in therefined pulp varies appreciably in the content of unsaponifiable matter,and thus also as regards the proportions of oil soluble, unsaponifiable,interiacially active material and of saponifiable matter which will beinterfacially active in the water soluble, saponified state. Acomparison of the compositions of ether extracts from refined pulpsprepared from different woods and having the same total amounts of etherextract follows:

TABLE I Comparison of composition of ether extracts of refined chemicalpulp prepared from difierent woods Percent of Material Present Based onBone Dry Pulp Such figures as given above are also somewhat dependent onthe process by which the pulp is made.

The two classes of extractable materials which are interfacially activeor which can become interiacially active have different physical andchemical properties and exercise different effects in the subsequentutilization of the pulp, as in its conversion into various cellulosicproducts in the chemical and rayon industries. Some of these effects aredesirable while others are not, but uniformity of effect is verydesirable.

I have discovered that the behavior of the refined wood pulp in itsconversion into various cellulosic products cannot be predicted on abasis of the amount of residual ether extract considered as a whole. Ihave found, for example, that hemlock and southern pine pulps eachhaving the same quantity of ether extract, say 0.15%, have the sameproperties because the hemlock pulp will contain a higher proportion ofether extractable, unsaponifiable matter. The hemlock pulp thus containsa higher proportion of oil soluble, unsaponifiable, interfacially activematerials and a lower proportion of saponifiable matter, interfaciallyactive in the water soluble, saponified state.

It is accordingly one of the objects of my invention to provide arefined wood pulp containing uniform quantities of either saponifiablematter, interfacially active when saponified, or unsaponifiableinterfacially active ether extractable matter, or both, regardless ofthe kind of wood from which the pulp was produced.

In accordance with the method of my invention, I attain uniformity ofpulp composition with respect to ether extract by ascertaining the kindsand proportions thereof in the pulp and then adding the required amountof synthetic, oil soluble, unsaponifiable, interfacially activematerials of a type not found in nature or saponifiable fatty or resinacid soap-forming materials (either as such or as their effectiveequivalents in the form of saponified soaps), to

do not 7 produce a pulp with a uniform amount of either one or bothtogether as required.

In practice the invention is applied to wood pulp containing not over0.15% of natural ether extractable matter consisting of saponifiable andnot over 0.07% of oil soluble, unsaponifiable matter. The adjustment ofsaponifiable and unsaponifiable matter to predetermined value is carriedout such that the total amount of unsaponifiable matter, both naturaland synthetic does not exceed 0.07%.

The unsaponifiable, oil soluble compounds used as additives in myinvention are in general ethylene glycol monoethers of high molecularweight alcohols. These agents, described later in detail, are purelysynthetic and do not occur at all as natural constituents of pulp etherextracts.

The synthetic, unsaponifiable compounds are extremely eifective inregard to their interracially active properties. The compounds are ingeneral relatively inexpensive as compared with natural, unsaponifiable,oil soluble, interfacially active materials. Furthermore, as syntheticcompounds, the compounds of the invention have the advantage of beingreadily producible in a pure and uniform state.

The refined wood pulps applicable to use in the invention, such as theso-called dissolving pulps, usually contain less than 0.07% ofunsaponifiable ether extractable matter. The invention, however, isespecially and advantageously applicable to those pulps containing arelatively low percentage of unsaponifiable ether extractable matter,say less than 0.02%, wherein substantial additions of the synthetic oilsoluble, un-

saponifiable compounds are necessary to attain a uniform content of saidmatter, not greater than 0.07%, in all species of refined wood pulp.

As heretofore pointed out, the amount 0;" unsaponifiable etherextractable matter has been chosen as a standard rather than the exactamount of unsaponifiable, ether extractable, interfacially active matterin that the former serves as a relative indication of the amount of thelatter and may be much more readily determined.

While it will be readily obvious to anyone skilled in the art how todetermine ether extractable unsaponifiable matter, nevertheless forclarity, I give the standard procedure which follows: 350 gm. of pulp ofknown moisture content, usually about l-8% moisture, is extracted 8hours with ether in a Soxhlet extractor. The ether is evaporated oh theextract solution and the residue may be weigh-ed if desired to determinethe total amount of ether extractable matter. The residue from the etherevaporation is then refluxed with cc. normal alcoholic KOl-i for 1 hour.The solution is then transferred to a separatory funnel, an equalquantity of water added and the unsaponifiable matter extracted withether. The ether solution is washed with water, dried by addition ofanhydrous NaZSOA, after which the solution is filtered, the sodiumsulfate being discarded after being washed with other. The ether isevaporated off and the residue heated 1 hour at C., then cooled andweighed. The value for other extractable unsaponifiable matter soobtained is then calculated the per cent on bone dry pulp.

Wood pulp as usually prepared as a source of cellulose for the viscoseindustry is of various degrees of purity, and is generally supplied foruse in the form of sheets. Normal dissolving wood pulp in present useconsists mainly of cellulose and contains an appreciable amount ofnon-cellulosic impurities, such as hemi-celluloses, fats, resins, waxes,etc. One of themain'objects in the manufacture of highlyrefined-dissolving pulp is to remove as much as possible of thenon-cellulosic impurities so that a whiter, purer pulp results which iscapable in the manufacturing of rayon of prcducinga higher grade yarn.

As described in U. S. Patent Re. 22,489, not all of the non-cellulosicimpurities which can be removed are undesirable from the standpoint ofviscose processing, and in fact certain of such impurities, normallypresent in small amounts, act beneficially as emulsifying agents in thestep of emulsifying or dispersing oils or pigments in the viscose. Thesebeneficial impurities which have been known to act as emulsifying agentsare surface active materials of the anion active class or materialswhich can give rise to the production of such surface active materialsduring the processing of pulp into viscose. .In a pulp whichhas not beenhighly refined most of these beneficial impurities constitute aportionof the materials removed by organic. solvents, as for example,ether, benzene, alcohol, etc. These impurities which actas anion activeemulsifying agents are of the nature of fats, oils, fatty acids, rosinand resin acids, all of which become incorporated in the viscose assodium soaps.

In theory, the problem of making a good pulp for viscose processingcould be solved by removing all the undesirable impurities whileretaining in suitable amounts those impurities which facilitate thesteps of emulsification and other processing steps. Under suchtheoretical conditions, the impurities which it would be desired toretain in suitable amounts from the standpoint of emulsifioation wouldbe of two quite different types:

1. The natural oils, fats and fatty acids, rosin and resin acids, whichin the viscose process form soaps. Such soaps in addition to improvingthe processing of the pulp into viscose, also due to their presence inthe .viscose, act as emulsifying agents.

2. The natural interfacially active materials soluble in oil andinsoluble in water heretofore described in detail. These materialsfunction as stabilizers of emulsions produced by the acid of anionactive agents.

In practice such a clean-cut separation is difficult to accomplishdirectly. Better results are obtainable by removing most or all of theimpurities, including the unsaponifiable ether extractable matter, andthen incorporating in the viscose small amounts of the syntheticunsaponifiable compounds of the invention. Where the content of naturalsoap-forming, emulsifying materials is low, anion active materials mayalso be added in accordance with Patent Re. 22,489.

In refined wood pulps, the unsaponifiable portion of the etherextractable matter will generally fall below 0.07%. While my inventionis applicable to use in cellulosic solutions prepared from refined woodpulp containing not more than 0.07% ether extractable unsaponifiablematerial, the advantages of adding the unsaponifiable, oil soluble,interfacially active material according to the invention are especiallygreat when the pulp contains less than 0.02% unsaponifiable material.

In accordance with this phase of the invention, a small quantity of thesynthetic unsaponifiable compound of the invention is incorporated inthe cellulosic material used in producing a viscose solution,,at leastprior to. completion .of shredding phases.

a scum to separate.

the alkali cellulose, and preferably to "the pulp prior-to use, toimprovethe characteristics of the spinning solution, particularly withregard to emulsification with opacifying agents.

Since the synthetic unsaponifiable, oil soluble, interfacially activematerials are insoluble in water or dilute caustic sodathey becomedispersed in a finely divided conditioniin the viscose. 'Since thematerials are oil soluble, they are thus in part extracted fromsuspension in the aqueous viscose phase by means of the oildropletsduring the emulsification process. .In order for this extractionprocess to take place an efficient degree, it is not only necessaryforthe materialsto be oil soluble but also thattheybe substantially waterinsoluble.

The synthetic unsaponifiable compounds which I add in practicing myinvention, like conventional surface active materials, arehydrophiliclipophilic combinations. These compoundshave a stronglipophilic group of. a hydrocarbon-character, together with agroupfhaving a relatively weak hydrophilic effect. Thus, theinterfacially active unsaponifiablecompounds used in my invention are atleast slightly oil soluble but substantially water insoluble. While thehydrophilic effect is not enough for the compounds to be appreciablysoluble in water, there is nevertheless a substantial attraction forwater. Hence the compounds will tend .to concentrate wherever there isan oil-water interface with the lipophilic portion dissolved in thewater.

The compounds used inmy invention do not greatly lower the surfacetensions of any oils they dissolve in. Being substantially insoluble inwater or aqueous solutions, they do not appreciably lower the'surfacetension of aqueous Nevertheless, when present at an oilwater interfacethey produce very low interfacial tensions.

In general, the unsaponifiable materials or compounds are ethyleneglycol monoethe'rs of high molecular weight alcohols, i. e., of alcoholscontaining at least 8 carbon atoms. The alcohols are hydroxylsubstituted hydrocarbons and may be aliphatic (straight or branchedchain, saturated or unsaturated) or cyclic. They may be primary,secondary, or tertiary. I prefer to use high molecular weight aliphaticalcohols (branched chain or straight) containing 8-4-8 carbon atoms. Theethylene glycol monoethers may be prepared me manner similar to thatgenerally employed in manufacturing lowermolecu- 1.2)1' weight glycolmonoethers such as are used in solvents (e. g., the methyl, ethyl orbutyl monoether of ethylene glycol). Thus, for example, an alcoholcontaining at least eight carbon atoms may be reacted with an equivalentamount of ethylene oxide to give aproduct predominating in the monoalkylether of ethylene glycol.

The following unsaponifiable, oil soluble, interfacially activecompounds are examples of compounds which may be used in the practice ofmy invention:

Ethylene glycol monoether of octyl alcohol (2- ethylhexanol) Ethyleneglycol monoether of vtetradecyl alcohol (7 -ethyl-2-methylundecanol-4)Ethylene glycol monoether of oleyl alcohol.

When viscose is emulsified with mineral oil, even if the oil particlesare relatively fine, if the emulsions. are not completely stable, therewill be a tendency for the emulsions tocream or for -In,the viscoseindustry such scums ,are extremely tr.o ublesome ;in that they tend tocollect in various lines and tanks and may or by means of a rotatingroll partly immersed work into the spinnerets where they will cause insuch an emulsion or dispersion. If desired, inferior or spoiled yarn. Ihave found that such the unsaponifiable, oil soluble, interfaciallyacscums tend to occur when the amount of ether tive compounds may beincorporated in the pulp extractable unsaponifiable material in the pulpprior to sheet formation as, for example, by is low, i. e., when suchmaterial is below 0.07% making additions to a suspension of pulp in andespecially when in the range of 0 to 0.02%. water in a stock chest. Insuch cases the scum will still be obtained even The application of theunsaponifiable matewhen anion active emulsifying agents are added rialsor compounds to the pulp may be accomto aid the emulsifying step.plished by use of a solution of the compound A convenient laboratorytest indicative of the in a satisfactory organic solvent but morepracrelative amounts of scum obtainable in comtically, from aneconomical standpoint, by use mercial operations with oil-opacifiedviscose from of an aqueous emulsion as described above. The differentpulp samples follows: 800 gm. of viscose preparation of such an aqueousemulsion may is emulsified for 5 minutes with 0.4% mineral oil 5 beeifected by any appropriate procedure combased on viscose using a smallbladed paddle remon to the art, generally in the presence of volving at4000 R. P. M. Portions of the freshly a small amount of a water solubleemulsifying emulsified viscose samples are then centrifuged agent. for 1hour at a force of 1500 x gravity. The For application during theshredding operation, amounts of scum which may separate out as thecompounds may be sprayed directly onto layers on the tops of tubes fromvarious viscose the alkali cellulose as a concentrated solution samplesare compared. in a suitable organic solvent, preferably a water When theunsaponifiable material is added miscible, volatile solvent such asethyl alcohol according to the invention to pulps that would orisopropanol. They may also be sprayed into normally give scum in theabove test, scum is the shredder as a concentrated emulsion or liqeithercompletely eliminated or greatly reduced. uid compounds may be employedin undiluted In addition microscopic examinations show that form. theaddition of the unsaponifiable material Where the total etherextractable content of greatly improves the emulsion characteristics,the pulp is very low, in addition to adding the imparting greaterstability of particle size, greater unsaponifiable compounds of theinvention, uniformity and smaller average particle size. there may alsobe added according to Patent That scum formation is due to a lack ofnatural Re. 22,489 fatty or resin acid soap-forming maunsaponifiableether extractable material may be terials or their effective equivalentsin the form seen from the following table. The table also of the anionactive, water soluble saponified shows the remarkable effect onreduction of scum soaps. Also other anion active agents may be byaddition of a small amount of the ethylene glyadded according to PatentRe. 22,489. When col monoether of '7-ethyl-2-methylundecanol-4. suchmaterials are added in a water soluble,

TABLE II Effect on scum in viscose emulsions of unsaponifiable portionsof pulp ether extractable matter and of an oil soluble, ethylene glycolmcnoether of an aliphatic alcohol (ethylene glycol monoether of 7-ethyl-2-methyZuncZecano1-4) Amount and Source of Amount and Source ofPulp Used Unsaponifiable Ether- Saponifiable Ether Amount of ScumObtained in Scum Cen- Extractable Material Extractable Material Itrifuge Test #1 Pulp 0.034% Natural..- 0.057% Natural Trace of Scum.

#2 Pulp 0.013% Natural... 0.065% Natural... Heavy Scum.

#2 Pulp lrnpreg. with 0.05% of Unsaponifiable Ether 1311- {0.034%Natural.-. 0650/ Natural Very Small Trace of tractable Material from #1Pulp. +0.05% from #1 Pulp j Scum.

#2 Pulp Impreg. with 0.05% of Saponifiable Ether Extract- 0 0137 Natural{0.065% Natural }Heavy Scum, addition able Material from #1 Pulp. 00.05% from #1 Pulp having no eifect.

#3 Pulp, being of the same manufactured type as #2 Pulp.-... 0.005%Natural... 0.025% Natural. Heavy Scum.

#3 Pulp Impreg. with 0.027 ethylene glycol monether of 7- {00057Natural...

ethyl2-mcthylundccanol i. 0,02% 301511101 1 l The oil soluble ethyleneglycol monoethers of anion active condition, it will frequently be con-No Scum.

aliphatic alcohols may be incorporated in the venient to emulsify theunsaponifiable, oil solufinished wood pulp, or during the formation ofble, interfacially active materials in a solution the pulp sheet orduring the viscose processing, of the anion active compound. Of theanion prior to the completion of shredding. Since active or potentiallyanion active compounds, the materials are not soluble in water, it isnot the most suitable are the saponifiable soappractical to add themdirectly to the viscose. forming materials (fatty or resin acidmaterials) Such direct addition gives an unsatisfactory disor theirefiective equivalents in the form of the tribution of the material inthe viscose so that saponified soaps.

if the viscose is subsequently emulsified, the With highly refined pulp,as the ether extractemulsion will not be satisfactorily stabilized. ablematerial approaches zero, if only the un- A most practical andconvenient method of sesaponifiable, oil soluble, interfacially activecomcuring the presence of the desired amount of pounds are added withoutanion active comunsaponifiable material in the viscose in a satpounds,some improvements are obtained but the isfactorily fine state ofsubdivision is to incoradvantages of the invention are obtained onlyporate the compound in the wood pulp. Such in part.

an addition may be advantageously effected to In the preferred form ofthe invention, in addithe pulp on the sheet forming machine subtion tothe glycol ethers of aliphatic alcohols, sequent to sheet formation butprior to complete anion active compounds will be present, either dryingby spraying the pulp sheet with an through their presence in naturalform in the aqueous emulsion or dispersion of the compound etherextractable material or by addition.

While the synthetic unsaponifiable, oil soluble, glycol monoethers usedin this invention are especially suitable for use in combination withanion active or potentially anion active compounds, they are alsosuitable for use in combination with cation active compounds, nonionicsurface active compounds and mixtures of these.

Since the amount of unsaponifiable ether extractable matter varieswidely in pulps from different woods, the invention makes it possible toimpart to pulp from one wood many of the processing characteristics ofpulp from a different wood. In this way, I can produce a uniform refinedwood pulp; in other words, an industrially uniform compositeirrespective of the many different kinds of Woods from which itoriginates.

While scum formation is not normally encountered in bright(nondelustered) viscose, use of pulp treated with an unsaponifiablecompound in the manner of the invention is, however, also advantageousin the preparation of bright viscose. Such treatment minimizes foamingand occlusion of air in'the viscose during the various mixingoperations. Treatment of the pulp with the glycol ethers of aliphaticalcohols of the invention is especially desirable when treating the pulpaccording to Patent Re. 22,489 with soaps which tend to promote foamingof the viscose. Thus, for example, the unsaponifiable compound can beemulsified in sodium oleate solution and the emulsion used to treat thepulp sheet either on the dryer of the pulp machine or in a sub sequentoperation.

When viscose is emulsified with oil for the preparation of delusteredrayon, the oil constitutes only a very small portion of the delusteredmaterial. Accordingly, since the unsaponifiable compounds dissolve inthe oil rather than in the aqueous phase only extremely small quantitiesof them are required, the effective range of the unsaponifiablecompounds being such as to give a total content of unsaponifiablematter, including both natural ether soluble and the synthetic glycolethers of from 0.01 to 0.07% and preferably from 0.02 to 0.05%. Sincethe unsaponifiable materials or compounds are not truly soluble in theviscose but rather disperse, with more than 0.07% of such materials,some material may tend to separate out in the viscose, particularly withbright viscose. Accordingly, it is important that the compounds be addedonly in extremely small amounts as specified. The percentages usedherein are based on the bone dry weight of the pulp.

This application is a continuationin-part of my application SerialNumber 601,063, filed June 22, 1945, U. S. Patent 2,518,680 and myapplication Serial Number 631,223 filed November 27, 1945, U. 5. Patent2,516,113.

I claim:

1. The method of improving refined wood pulp containing not over 0.15%of natural ether-extractable matter, of which less than 0.07% isoil-soluble unsaponifiable matter, which comprises adding to suchrefined wood pulp an ethylene glycol monoether of an aliphatichydroxyl-substituted hydrocarbon having from 3 to 18 carbons atoms, theamount of the added monoether of the substituted hydrocarbon being suchas not to cause said oil-soluble, unsaponifiable matter to exceed about0.07%, based on the bone dry weight of the pulp.

2. The method of claim 1 in which the amount 10 of the added monoetherof the substituted hydrocarbon is such as not to cause theether-extractable matter in the pulp to substantially exceed 0.15%,based on the bone dry Weight of the pulp.

3. The method of claim 1 in which the monoether of the substitutedhydrocarbon is ethylene glycol monoether of 7 ethyl 2 methylundecanol-4.

.4. The method of claim 1 in which the monoether of the substitutedhydrocarbon is ethylene glycol monoether of oleyl alcohol.

5. The method of claim 1 in which the monoether of the substitutedhydrocarbon is ethylene glycol monoether of 2-ethy1 hexanol.

6. The method of improving refined wood pulp containing not over 0.15%of natural ether-extractable matter, of which less than 0.07% isoilsoluble unsaponifiable matter, which comprises adding to such refinedwood pulp an ethylene glycol monoether of an aliphatichydroXyl-substituted hydrocarbon having from 8 to 18 carbon atoms, andat least one compound of the group consisting of soap-forming fattyacids, soapforming resin acids, and the water-soluble sodium salts ofsaid acids, the amount of the monoether of the substituted hydrocarbonbeing such as not to cause said oil-soluble unsaponifiable matter toexceed about 0.07% based on the bone dry weight of the pulp, and theamount of the monoether of the substituted hydrocarbon and the member ofsaid group added being such as not to cause the ether-extractable matterin the pulp to substantially exceed 0.15%, based on the bone dry weightof the pulp.

7. In the production of cellulosic products having an opacifying agentincorporated therein from wood pulp having not over 0.15% of naturalether-extractable matter, both saponifiable and unsaponifiable, of whichless than 0.07% is oilsoluble unsaponifiable matter; the improvementwhich comprises adding to the wood pulp an ethylene glycol monoether ofan aliphatic hydroxyl-substituted hydrocarbon having from 8 to 18 carbonatoms, the amount of such monoether of the substituted hydrocarbon beingsuch that the total amount of ether-extractable, unsaponifiable matterin the wood pulp does not exceed about 0.07 based on the bone dry weightof the wood pulp, whereby in the subsequent processing of the pulp intothe cellulosic product, said opacifying agent is dispersed in thecellulosic product without objectionable scum formation.

8. In the production of cellulosic products as defined in claim 7 inwhich the monoether of the substituted hydrocarbon is ethylene glycolmonoether of 7-ethyl-2-methyl-undecanol-4.

9. In the production of cellulosic products as defined in claim 7 inwhich the monoether of the substituted hydrocarbon is ethylene glycolmonoether of oleyl alcohol.

10. In the production of cellulosic products as defined in claim 7 inwhich the monoether of the substituted hydrocarbon is ethylene glycolmonoether of 2-ethyl hexanol.

11. In the production of cellulosic products having an opacifying agentincorporated therein from wood pulp having not over 0.15% of naturalether-extractable matter, both saponifiable and unsaponifiable, of whichless than 0.07% is unsaponifiable matter; the improvement whichcomprises adding to the wood pulp an ethylene glycol monoether of analiphatic hydroxyl-substituted hydrocarbon having from 8 to 18 carbonatoms and at least one compound from the group consisting ofsoap-forming fatty acids, soap-forming resin acids, and thewater-soluble sodium salts of said acids, the amount of the monoether ofthe substituted hydrocarbon being such as the total amount ofether-extractable unsaponifiable matter in the pulp does not exceedabout 0.07% based on the bone dry weight of the wood pulp and the totalamount of the monoether of the substituted hydrocarbon and the member ofsaid group added to the pulp being such that the total amount ofether-extractable matter in the pulp does not substantially exceed 0.15%based on the bone dry weight of the wood pulp, whereby in the subsequentprocessing into the cellulosic product, said opacifying agent isdispersed in the cellulosic product without objectionable scumformation.

12. A refined wood pulp containing natural and added ether-extractablesaponifiable matter and ether-extractable oil-soluble unsaponifiablematter totaling not substantially over 0.15% based on the bone dryweight of the wood pulp, the added ether-extractable oil-solubleunsaponifiable matter being an ethylene glycol monoether of an aliphatichydroxyl-substituted hydrocarbon having from 8 to 18 carbons atoms, thetotal amount of ether-extractable oil-soluble unsaponifiable matter inthe pulp not substan- 12 tiall exceeding 0.07% based on the bone dryweight of the pulp, said pulp also containing at least one addedcompound from the group consisting of soap-forming fatty acids,soap-forming resin acids and the water-soluble sodium salts of saidacids.

13. A refined wood pulp as defined in claim 12 in which the monoether ofthe substituted hydrocarbon added to the wood pulp is a com poundselected from the group consisting of ethylene glycol monoether of7-ethy1-2-methylundecanoli, ethylene glycol monoether of oleyl alcohol,and ethylene glycol monoether of Z-ethyl hexanol.

14. A refined wood pulp as defined in claim 12 in which the addedether-extractable saponifiable matter is a compound from the groupconsisting of soap-forming fatty acids, soap-forming resin acids and thewater-soluble sodium salts of said acids.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,423,469 Schlosser et a1. July 8, 1947 2,432,129 Schlosser eta1. Dec. 9, 1947 2,451,558 Schlosser et al Oct. 19, 1948 2,491,499Katzen Dec, 20, 1949 2,518,680 Gray Aug. 15, 1950

12. A REFINED WOOD PULP CONTAINING NATURAL AND ADDED ETHER-EXTRACTABLESAPONIFIABLE MATTER AND ETHER-EXTRACTABLE OIL-SOLUBLE UNSAPONIFIABLEMATTER TOTALING NOT SUBSTANTIALLY OVER 0.15% BASED ON THE BONE DRYWEIGHT OF THE WOOD PULP, THE ADDED ETHER-EXTRACTABLE OIL-SOLUBLEUNSAPONIFIABLE MATTER BEING AN ETHYLENE GLYCOL MONOETHER OF AN ALIPHATICHYDROXYL-SUBSTITUTED HYDROCARBON HAVING FROM 8 TO 18 CARBON ATOMS, THETOTAL AMOUNT OF ETHER-EXTRACTABLE OIL-SOLUBLE UNSAPONIFIABLE MATTER INTHE PULP NOT SUBSTANTIALLY EXCEEDING 0.07% BASED ON THE BONE DRY WEIGHTOF THE PULP, SAID PULP ALSO CONTAINING AT LEAST ONE ADDED COMPOUND FROMTHE GROUP CONSISTING OF SOAP-FORMING FATTY ACIDS, SOAP-FORMING RESINSAND THE WATER-SOLUBLE SODIUM SALTS OF SAID ACID.